On one side stand the fiscally and socially conservative purists -- party activists and elected officials who maintain that Republicans need to adhere to strict principles to emerge as a strong opposition party.

On the other side stand the beleaguered Republican moderates, the dwindling number of blue-state GOPers and -- less quietly -- key members of party leadership on Capitol Hill.

They maintain that the party can't afford to cut itself off from any blocs of voters, not with a popular Democratic president in office. They warn that the wrong moves now will consign the Republican Party to a prolonged minority status, chasing a shrinking base in ever-smaller portions of the country.

"There is no plausible scenario under which Republicans can grow into a majority while shrinking our ideological confines and continuing to retract into a regional party," Sen. Olympia Snowe, R-Maine -- now one of only three Republican senators from the Northeast -- wrote in the New York Times on Wednesday.

Specter's situation, of course, is unique. He was a moderate senator whose state has grown increasingly Democratic over his three decades in the Senate.

Specter acknowledged as much in his decision to become a Democrat. But in leaving the GOP, he bemoaned what he described as the party's conservative shift: "Since my election in 1980, as part of the Reagan big tent, the Republican Party has moved far to the right."

Ramifications of Specter's Switch

Specter's defection has huge potential short-term ramifications. With the expected victory of Al Franken in Minnesota, Democrats now stand on the verge of securing 60 Senate votes -- enough to cut off any GOP filibuster.

But some in the party say they're not sorry to see Specter go. Not having a moderate like Specter -- who supports abortion rights and was one of only three GOP members of Congress to vote for the president's stimulus package -- makes it easier for the party to present a united front in opposing Obama.

"I'm happy not to have an Arlen Specter -- a potential traitor at all times -- who can sink Republican messaging because of his ego," said Rick Wilson, a veteran Republican consultant. "He's not a guy who was here for the good of the team."

Obama remains extraordinarily popular in polls as a smaller portion of voters say they consider themselves Republicans. But voters are expressing concern about runaway spending and deficits -- leaving fiscal conservatives convinced that the way to regain voters' trust is through adhering to a strict message of fiscal discipline.

The recent "tea party" protests against the president's tax and spending plans offered a glimpse into the potential political power of government spending as an electoral issue, Wilson said.